Transforming growth factors (TGFs) are low molecular weigh peptides capable of stimulating non-transformed indicator cells to grow as colonies in soft agar. We have obtained the first evidence for the presence of such factors in the urine of patients with a variety of disseminated cancer. Chromatographic analysis of acidified urine aliquots indicates that the majority of cancer patients and only a few non-malignant controls contain a high molecular weight TGF activity with co-elutes with epiderman growth factor (EGF)-competing activity. In contrast, a low molecular weigh activity which does not co-elute with EGF competing activity was found in all urines tested. High molecular weight urinary TGF activity is currently being evaluated as a clinically useful biologic marker for disseminated cancer.